Today, many vehicles are constructed to include at least one exterior airbag, intended to be inflated in the case of a collision with moving objects, such as pedestrians, cyclists or animals and to alleviate the collision force that the moving object is subjected to.
In order to further minimize the damages afflicted to the moving object in the event of such an impact, it has been proposed to use some kind of hood lifting arrangements. These arrangements are generally constructed so that the rear part of the hood, i.e. the part closest to the windscreen, is lifted in the event of a collision with a moving object. Arrangements of this type are disclosed in for example W02007/067121 and EP2256007.
For any external airbag system to operate properly, a robust sensing system is necessary. Unlike crash sensors which trigger deployment while the vehicle is crushing and decelerating, the sensing system for an external airbag may anticipate an impact before it has occurred. This critical “Time Before Collision” is related to the time to deploy the actuator (e.g. 30-200 ms) and the clearance distance in front of the vehicle (e.g. 100-800 mm). Inadvertent deployment is not only costly but may temporarily disable the vehicle. Moreover, since the deployment of an airbag is achieved through a release of energy, deployment at an inappropriate time may result in undesirable effects. This invention is related to a sensing system for an external airbag safety system which addresses these design concerns.
Radar and ultrasonic detection systems have been studied and employed for motor vehicles for many years. Radar systems for motor vehicles operate in that a radio frequency signal, typically in the microwave region, is emitted from an antenna on the vehicle and the reflected-back signal is analysed to reveal information about the reflecting target. Such systems have been considered for use in active braking systems for motor vehicles, as well as obstacle detection systems for vehicle drivers. Radar sensing systems also have applicability in deploying external airbags. Radar sensors provide a number of valuable inputs, including the ability to detect the range to the closest object with a high degree of accuracy (e.g. 5 cm). They can also provide an output enabling measurement of closing velocity to a target with high accuracy. The radar cross section of the target and the characteristics of the return signal may also be used as a means of characterizing and identifying moving objects.
An alternative means for detecting and identifying moving objects is a vision system having one or more video cameras used for detecting objects. A vision system for a vehicle identifies and classifies objects located proximate a vehicle. The system includes a sensor array that produces imagery that is processed to generate depth maps of the scene proximate a vehicle. The depth maps are processed and compared to pre-rendered templates of target objects that could appear proximate the vehicle. A target list is produced by matching the pre-rendered templates to the depth map imagery. The system processes the target list to produce target size and classification estimates. The target is then tracked as it moves near a vehicle and the target position, classification and velocity are determined. A further alternative object detection system for a vehicle includes an infrared camera for gathering an image of at least a part of the surroundings of the vehicle; and a processor for applying an algorithm to at least a part of the image gathered by the camera, the algorithm identifying non-relevant hot or warm objects detected by the camera and reducing the brightness and/or distinctiveness of the non-relevant objects in the image.
A classification system is used for classifying objects in the vicinity of a vehicle. The system typically includes a video/infrared camera for gathering camera data, a reflected radiation system for gathering reflected radiation data, and a classifier. Raw data from the video/infrared camera and the reflected radiation system can be combined and analysed by the classifier, the classifier being configured to provide an output relating to the type of an object that appears in data gathered by both the camera and the reflected radiation system.
Existing object classifiers include computer programs which are operable to analyse data from a vehicle sensor, such as a camera or radar system. The classifier is trained with exposure to many different types of object in different circumstances, so that the program is able to make an accurate determination as to the type of a new kind of object that is detected. Known types of objects can be stored in a database for future reference. In the subsequent text, the term “pre-crash sensor” will be used for vehicle sensors hsving a camera or a radar/ultrasonic system.
A vehicle is also provided with one or more contact sensors, such as accelerometers or pressure sensors, for detecting an actual impact. In the subsequent text, the term “in-crash sensor” will also be used for this type of contact sensors. Modern vehicles can be provided with 5-10 contact sensors across a front bumper or similar suitable portion of the vehicle.
When it is determined by vehicle crash sensors that an impact is imminent, or that crash is occurring, one or more of these external safety systems may be deployed, or a safety system may be deployed in one of a plurality of possible modes, depending in part upon the type of the other object that is involved. If it appears that the vehicle is about to strike a pedestrian, then the external safety system in the form of an external air-bag and/or a bonnet (hood) lifter may be activated, but if the vehicle is about to strike an inanimate object such as a tree, then there is no need for these protection systems to be deployed. Accurate classification of objects in the vicinity of a vehicle is therefore desirable for vehicle safety systems to be activated in the most appropriate manner.
Although information obtained from pre-crash sensors yield valuable data, exclusive reliance upon a pre-crash sensor signal for deploying an external airbag has certain negative consequences. As mentioned previously, deployment of the external airbag is a significant event and should only occur when needed in an impending impact situation. Pre-crash sensors are prone to “false-positive” (FP) indications. These are typically due to phenomena such as a ground reflection, projection of small objects, and software misinterpretation, which faults are also referred to as “fooling” and “ghosting”. For example, a small metal object with a reflector type geometry can return as much energy as a small car and as such can generate a collision signal in the radar even when the object is too small to damage the vehicle in a substantial way. Also, there may be “near miss” situations where a target is traveling fast enough to avoid collision, yet the pre-crash sensor would provide a triggering signal for the external safety system.
The relative speed is a measure for the classification of objects. It can be used to establish, for example, whether the relevant object is at rest or whether it moves at a certain speed. Since pedestrians, for example, only have limited maximum speed, it is easy to distinguish pedestrians from vehicles. This may then be used in particular also to take into account the severity of an accident. Thus this makes it possible for the device according to the present invention to be able to make a triggering decision for the actuator system on the basis of speed. With the aid of speed information, the impact signal becomes easier to differentiate as to whether it involves a pedestrian, a cyclist or another object. Including the speed thus helps to prevent a false triggering of the actuator system. Overall this results in a more precise evaluation of the impact signal, that is, the signal from the contact sensor system. For example, a fast and light object may provide a similar impact signal as a slow and heavy object. This shows that the knowledge of the speed expands the decision space by a dimension such that a classification of the different objects is improved and thereby also the decision for triggering the actuator system. In the subsequent text, the term “pedestrian” should be interpreted as including any moving object for which the external safety system is suitable, i.e. pedestrians and cyclists, as well as animals.